Motorhome self build project. Built and designed by one person over the course of about 36 months. The base is a 1994 Carpenter school bus. The end result will be a low energy consumption motorhome.

Saturday, August 12, 2017

Naked in my motorhome

It's currently 86F in the bedroom of my motorhome. Stripping off naked and just being there in my birthday suit seems like a very good idea. I don't want to shock the lampshade though! I think I've probably gone as far as I can for the moment with cooling without investing in an AC unit.

In Walmart, there was a very nice AC unit. It was a window unit that measured about 13 inches high. That would fit quite nicely under the bus. I have heard these Arctic King units just aren't very powerful. That's fine because as far as I can tell, I don't need anything particularly powerful. If I can keep the summer temperature down to say 78 that should be fine. It would need some inventive ducting and an equally inventive bay to fit it into and there's no guarantee that I'd be able to get another similarly sized unit should it fail - which the naysayers keep telling me it will. For the moment then I shall stay with ventilation and removing excess clothing.

Over the last few days I've taken delivery of an aluminum box and have mounted the two plastic panel mount holders for my Chinese USB sockets. I've also added a voltmeter. There's a 12v cigarette lighter socket included also. Now, on order I have another Chinese USB socket. I will probably replace that 12v cigarette lighter socket with a USB socket. There's also a very nice green illuminated toggle switch that lights up green when it's switched on. That should provide a color clash enough to render even the hardiest soul violently ill. The sockets have blue lights, the switch is green and the voltmeter is red.

Looking at my cigarette lighter to 120v inverter I noticed that it's both 8.8A and only produces 120v at 0.75A. That would have a struggle to power a 100W light bulb! I have not checked the power requirement of my Maha battery charger but I would imagine it would be in excess of that even used straight off 12v.

The plan was to wire all the sockets and the voltmeter together under a single fuse on my distribution panel. That plan has changed several times. Adding up the maximum power, the dual USB sockets are 3.3A each. I have two which is 6.6A. Add a 3rd and I'd have 9.9A which would work well off a 10A fuse.

The voltmeter applied to the line coming in from the charge controller should always read 12v. Not much point in measuring that. The line coming in straight from the battery is the one to measure. That should tell me when the charge controller is about to kill the power. It might even be worth putting a second voltmeter just to measure the power from the inverter and measure both. That would bring me down to four USB sockets, two of which are 1.1A and two of which are 2.2A.

I have to thank EngineeringToolbox.Com for the table above. Normally I just use "wire" for 12v applications and never have a problem. On the other hand I'm usually using very low amperages. I'll be putting a 30A cable to my big battery despite the fact my draw will be minimal. So, what will my draw be?

2.5A extraction fan

2 x 0.5A CPU fans.

2 x 3.3A USB sockets

That's a grand total of under 11A. Assuming I add two more CPU fans and two more USB sockets (the car store has better looking USB sockets) that's an extra 7.6A or if both sockets are USB 2 then 5.4A. So I'm looking at under 20A maximum draw.

Yes, you are correct - I do have a 12V socket. That's going bye bye though for this particular project. It will be returning as an inlet for extra solar or wind power where it'll be mounted straight onto the side of the bus.

Switching down to two dual USB sockets and two voltmeters was the work of a few seconds. It had the effect of reducing current draw to a maximum of under 7A. That still means 14ga wiring for the positive side of the two USB hosts and one voltmeter. The other voltmeter will be powered directly from the battery. That way I get to see the voltage on both sides of the charge controller. The power switch will have to be changed to a straightforward plain switch but be on the common ground side.

With that all sorted out, I have a delay in waiting for my piggyback spade connectors to arrive and because I need to buy some 12 - 14 gauge wire. Testing the connection of the battery ground to the charge controller supply ground produced no immediate ill effects. Nothing went boom and nothing went up in smoke. That was when I tried it on one charge controller. The other was a different story.

The extraction fan was off due to low voltage. I connected the negative to the negative and the fan roared into life. That's not what I expected and isn't desirable either. Clearly I'm going to have to work this differently. As I've already drilled my holes in the aluminum box, it's hard to undrill them. Fortunately socket blanks exist for this purpose.

Hunting though my parts supply I found loads of on-off-on switches that were of no particular use for this project. I found a few lighted on-off switches that again were of no particular interest. A double pole single throw or double pole double throw would have been advantageous but none were in my supplies. I did, however, find a make contact pushbutton switch and a straightforward on-off single pole toggle switch. Now I can put the switches on the positive side where they should be.

Well, I went shopping and bought some 12 gauge wire only to find it's about the same size as some cable I already have that's not labelled. That's fine - at least I know what I have. I didn't find any replacement switches but decided in the end to go ahead with a pushbutton switch for the battery monitoring on the basis that monitoring will be fairly inaccurate on the battery anyway. Lead-acid batteries need to rest for 30 minutes before the voltage and hence charge level can be correctly assessed.

In vain I hunted for some piggyback connectors. Those I ordered I figured would not arrive today and yet they did. Thus I was lucky not to have paid through the nose for a second set. I'm determined to complete my USB power block installation today!

Today's massive shopping expedition included two kinds of bracket to hold my USB power block in place, two colors of 12 awg cable, a can of liquid insulation and a can of paint. My blue piggyback connectors also arrived in the post. Thus, I'm all set for this project.

While I was in Walmart I saw a $10 faucet that would fit my handbasin. I didn't buy it because that's not a project due to be undertaken until winter. Winter has two projects or perhaps three. I need to put cold water plumbing in from a hose connection. That will feed to the cold of my faucet. The other project is to put in two 120v lines. One will go to the inside of my cupboard (if I really can fit a portable AC unit in there) and the other will go to under the handbasin where there will be an instant hot water heater. I had thought about plumbing from the heater to the shower but decided the easiest way is just to put an extra faucet under the sink with a connection to the hot water so that I can fill the cooler that i use with my shower pump. There's less construction involved.

On my return from the store, I'd disconnected the batteries from my charge controllers but the lights on one were flashing away. It seems it still puts solar power through. One of my fans was spinning lazily. Clearly I've got to put a solar disconnect in as well as a battery disconnect. Just think... when the aliens invade, they won't be able to pick me up because I can turn all of my electrical devices off. The only other thing I'll need is a tinfoil hat to stop them picking up my brainwaves. I believe they're sold alongside the August 21st 2017 USA Eclipse glasses.

The first thing I did was to put the pushbutton switch in place. That had to be shaved down on one side to make it fit. Now that is a Radio Shack switch and shame on Radio Shack, it isn't a standard spade connection. In fact, after trying it with midget-sized spade connectors, I can rule those out too. Radio Shack has just forced me to solder that connection though why, I don't know as it would have taken barely a fraction of a fraction of a fraction of a cent to make the tags big enough to offer the choice of solder or midget spade.

Next came the delay. Looking at my brackets, they were shiny metal - possibly tin plated. That meant I had to use a self-etching primer before painting them. They're what's going to hold my box in place. I'll rivet them to the sides of the box and screw the box to a cross beam. I'll have to sit what I'm charging on top of the counter or perhaps on top of the microwave. I'm assuming that if I'm solar charging things then the microwave is packed away because I'm dry camping.

The piggyback connectors are definitely the business. They make connecting my USB ports in parallel, a real breeze. I think I always underorder connectors. I've had to reorder several times. I seem to be on the right track. Since I'd got this far, I connected the unit to a battery and it worked well. Both USB chargers lit and the voltmeter lit. There was a heck of a crackle as I connected to the electricity but that's only to be expected. The switch currently is upside down and will have to be removed and rotated. That's a matter of seconds work at this stage though.

As can be seen, it's looking pretty good. The goal is to have solar charged USB devices. While I work in the bus, I can charge my phone or my tablet or my MiFi pad (should Straight Talk MiFi ever become a viable option again). I heartily wish somebody would produce a straightforward flip phone that could be turned into a hotspot. I don't want a clunky great big smartphone. I want something with decent battery life.

That was pretty much it for the day. By the time I'd done all that, dusk was falling. That brings me to two questions people keep asking me:
1. Why is the bus taking so long? Simply because I have a life to live around doing it and I want to get things right.
2. Why are you spending so much time on the bus. The answer to that is more complicated. I need to get it done and done as quickly as I can. My mother never lived to see its completion and always considered it to be some kind of hobby anyway. My dad's not quite sure that it's not a hobby but I want to show him it's completed, titled as a motorhome and that I've used it for a trip or two. Concurrent with that, a friend who's on his last legs is going to Canada in a few weeks and will spend 3 months there, during which time I hope to be able to drive somewhere in my motorhome to meet him.